what time is the last train from shanghai pudong airport to the city (let's say east nanjing stn)?

Well, according to your arrival time, there is no subway at the airport. But don't worry.
You can take airport shuttle bus Night Line, get off at East Yanan Road Middle Zhejiang Road. This bus line operates from 23:00 to the arrival of the final flight. After arriving, take a taxi to East Nanjing Road. The cab fare is about CNY 20 in the night.